The present invention relates to a modular hydraulic actuator for a valve.
Hydraulically actuated valve assemblies are often used in the oil industry, among other uses, to control the flow of oil. In a typical assembly 20 having a double-acting hydraulic actuator 22 for example, as shown in FIGS. 1 and 2, a piston 24 inside the actuator 22 is driven on either side by pressurized hydraulic fluid entering either of two hydraulic fluid ports 26, 28. Pressurized hydraulic fluid entering the cylinder 30 through the upper port 26 causes the piston 24 to move down (away from the upper port 26). Because an operating stem 32 is coupled to the piston 24, downward movement of the piston 24 causes downward movement of the operation stem 32, which in turn causes downward movement of a gate 34 coupled to the other end of the operating stem 32. Similarly, pressurized hydraulic fluid entering the cylinder 30 through the lower port 28 causes the piston 24, as well as the operating stem 32 and gate 34, to move upward.
Therefore, one end 36 of the operating stem is exposed to pressure within the cylinder 30 from the pressurized hydraulic fluid during actuation of the valve 34, which may be as high as 3000 psi, for example. The other end 38 of the operating stem 38 is exposed to pressurized fluids flowing through the valve 34, which can be as high as 30,000 psi. The operating stem is reciprocating up and down as valve opens and closes. The wear of the stem packing is directly proportional to the number of open/close cycles the valve experiences. The seals are non-metallic and therefore, experience quick wear. Thus, these seals 40 around the operating stem 32 need replacement quite often during the life of the assembly 20.
FIG. 2 shows an exploded view of the assembly 20 of FIG. 1. To access the seals 40 around the operating stem 32 at the lower portion of the actuator 22 shown in FIGS. 1 and 2 (e.g., for replacing the seals 40), at least the following steps are required (the order may vary). The six nuts 42 and corresponding studs 44 located about the hydraulic cylinder 30 are removed. Then the hydraulic cylinder 30 is removed and separated from the piston 24, which remains attached to the operating stem 32. A set screw 46 holding a centering pin 48 on the upper end 36 of the operating stem 32 is loosened or removed. The centering pin 48 is removed from the upper end 36 of the operating stem 32. The piston lock nut 50, which retains the piston 24 on the operating stem 32, is removed. The piston 24 is unscrewed and removed from the upper end 36 of the operating stem 32. Finally, the packing gland 52, which holds the stem packing 54 and other seals 40 in place, is unscrewed. With the packing gland 52 unscrewed and/or removed, the stem packing 54 and the seals 40 held by the packing gland 52 can be accessed and replaced, if needed.
Note that to get to the step when the packing gland 52 is unscrewed, the piston 24 had to be separated from the cylinder 30. Therefore, the piston rings or seals that provide a seal between one side of the piston 24 in the cylinder 30 and another become unseated when the piston 24 is separated from the cylinder 30. Thus, upon reassembly of the actuator 22, the piston rings and/or seals must be reseated or may even need replacement after being unseated. Reseating piston rings and seals when installing a piston 24 into a cylinder 30 is often a cumbersome procedure requiring special tools to ensure that the piston rings and seals seat properly and are not damaged in the process. Therefore, because accessing the packing gland 52 and its associated seals 40 in existing hydraulically actuated valve assemblies unnecessarily requires the piston 24 to be removed from the cylinder 30, there is a need for a hydraulically actuated valve assembly that allows the packing gland 52 and its associated seals 40 to be accessed without requiring the actuator 22 to be disassembled or without requiring that the piston 24 be removed from the cylinder 30.
Also, note that accessing the packing gland 52 and its associated seals 40 for replacement in the existing hydraulically actuated valve assembly 20 requires numerous steps and the removal of numerous parts. Typically, the packing gland 52 and its associated seals 40 are replaced in the field (e.g., on an oil rig platform). Because the environment in the field is not always conducive to the disassembly and reassembly of a complex device and parts can be easily lost, there is a need for a hydraulically actuated valve assembly that allows the packing gland 52 and its associated seals 40 to be accessed more easily, faster, and requiring fewer components of the actuator to be disassembled in the process.
Furthermore, in the field, often as many as a dozen or more hydraulically actuated valve assemblies may receive maintenance at one time. Thus, if numerous hydraulically actuated valve assemblies are disassembled and the parts for these get mixed together or mixed-up, the likelihood that a previously seated piston assembly will match or mate with a different cylinder may be low. A mismatch between a used piston assembly and a used cylinder can affect the performance of the actuator, and it may make reassembly difficult. Therefore, it would be better in most cases not to separate the piston assembly from its cylinder if it is not needed.
In addition, there are the economic considerations. The time that it takes to disassemble a hydraulically actuated valve assembly for maintenance requires production downtime, as well as labor time for skilled technicians in the field. Furthermore, there is cost involved with supplying special tools and training for these technicians to perform their tasks. Therefore, it is desirable to have a hydraulically actuated valve assembly where the packing gland and its associated seals can be more quickly and more easily accessed for maintenance, without the need to remove the piston from the cylinder.
The problems and needs outlined above are addressed by the present invention. In accordance with one aspect of the present invention, a modular portion of a hydraulic valve actuator is provided. The modular actuator portion comprises a hollow cylinder portion, a piston, a cylinder head portion, and a piston retainer portion. The cylinder portion has a first end and a second end. The piston is located in the cylinder portion, and the piston is adapted to slidably fit in the cylinder portion. The piston has a slotted portion formed therein. For example, the slotted portion of the piston may have a generally T-shaped cross-section. The cylinder head portion closes the second end of the cylinder portion. The piston retainer portion is located at an interior surface of the cylinder portion and at the first end of the cylinder portion. Part of the piston retainer portion extends radially inward relative to the interior surface of the cylinder portion farther than a portion of the piston such that the piston cannot slide completely past the piston retainer portion. Thus, the piston retainer portion keeps the piston within the cylinder portion when the modular actuator portion is operably assembled.
In other embodiments, the modular actuator portion may further comprise a cylinder retainer portion and/or a locking screw. The cylinder retainer portion is located along an outside surface of the cylinder portion and at the first end of the cylinder portion. The cylinder retainer portion has a plurality of screw holes formed therein. The locking screw extends at least partially through the cylinder head portion and is threadedly coupled to the cylinder head portion. The locking screw is adapted to press against the piston with an end of the locking screw to displace the piston when needed.
In other embodiments, the modular actuator portion may further comprise a handle, one or more hydraulic fluid ports, and/or a retainer ring. The handle may be removably coupled to a distal end of the locking screw. The one or more hydraulic fluid ports may extend through a wall of the cylinder portion and/or through the cylinder head portion. In other embodiments of the present invention, the cylinder portion and the cylinder head portion may be integral parts of a single component, the cylinder portion and the cylinder retainer portion may be integral parts of a single component, and/or the cylinder portion and the piston retainer portion may be integral parts of a single component. Alternatively, the cylinder portion, the cylinder retainer portion, the cylinder head portion, and the piston retainer portion may be separable parts.
In accordance with another aspect of the present invention, a modular hydraulic actuator is provided. The modular hydraulic actuator comprises a first modular actuation portion and a second modular actuation portion. The first modular actuation portion comprises a hollow cylinder portion, a cylinder retainer portion, a piston, a cylinder head portion, a locking screw, and a piston retainer portion. The cylinder retainer portion is located along an outside surface of the cylinder portion and at a first end of the cylinder portion. The cylinder retainer portion has a plurality of screw holes formed therein. The piston is located in the cylinder portion, and is adapted to slidably fit in the cylinder portion. The piston has a slotted portion formed therein. The cylinder head portion closes a second end of the cylinder portion. The locking screw extends through the cylinder head portion and threadedly couples to the cylinder head portion. The locking screw is adapted to press against the piston with an end of the locking screw to displace the piston. The piston retainer portion is located at an interior surface of the cylinder portion and at the first end of the cylinder portion. Part of the piston retainer portion extends radially inward relative to the interior surface farther than a portion of the piston such that the piston cannot slide completely past the piston retainer portion. The second modular actuator portion comprises a bonnet portion, an operating stem, and a nut. The bonnet portion has a central hole formed therethrough. The bonnet portion has a plurality of screw holes formed therein at one end of the bonnet portion. The bonnet portion screw holes correspond to the cylinder retainer portion screw holes. The operating stem extends through the bonnet portion central hole. The operating stem has a first end removably coupled to the valve member. The operating stem has a threaded second end. The nut has an exterior shape adapted to slidably interfit with the slotted piston portion. The nut has a threaded hole formed therein that is threadedly coupled with the threaded second end of the operating stem. The first modular actuator portion is removably coupled to the second modular actuator portion with a plurality of fasteners via the cylinder retainer screw holes and the bonnet screw holes. The first modular actuator portion can be separated from the second modular actuator portion without disassembling the first modular portion. Similarly, the second modular actuator portion may be separated from the first modular actuator portion without disassembling the second modular actuator portion.
Regarding other embodiments, the first modular portion may have one or more hydraulic fluid ports formed therein. The bonnet portion of the second modular portion may have a hydraulic fluid port formed therein. The slotted portion of the piston may have a generally T-shaped cross-section, and the exterior shape of the nut may have a generally T-shaped cross-section corresponding to the cross-section of the slotted piston portion. The second modular actuator portion may further comprise a packing gland threadedly coupled into the bonnet portion about the operating stem, wherein the packing gland is adapted to retain at least one seal. Also, the second modular actuator portion may further comprise a drift ring located about the operating stem and threadedly engaged with the bonnet portion for the purpose of limiting the stroke of the piston when the actuator is operably assembled. The bonnet portion may be adapted to removably attach to a valve housing. The plurality of fasteners may comprise cap screws, wherein the bonnet portion screw holes have threads formed therein adapted to threadedly engage with the cap screws. In alternative, the plurality of fasteners may comprise studs extending from the bonnet portion and fastener nuts adapted to threadedly engage with a threaded portion of the studs. Or, the plurality of fasteners may comprise bolts with accompanying fastener nuts.
In accordance with another aspect of the present invention, a hydraulically actuated valve assembly is provided. The hydraulically actuated valve assembly comprises a valve component and a modular hydraulic actuator comprising a first modular portion and a second modular portion. The valve component comprises a valve body and a valve member. The valve body has a plurality of screw holes formed therein. The valve member is located in the valve body and slidably fits in the valve body. The first modular actuator portion of the modular hydraulic actuator is as described above for the modular hydraulic actuator. As above, the second modular actuator portion comprises a bonnet portion, an operating stem, and a nut. The bonnet portion has a central hole formed therethrough, and has a first plurality of screw holes formed therein at a first end of the bonnet portion. The first plurality of bonnet portion screw holes corresponds to the cylinder retainer portion screw holes. The bonnet portion also has a second plurality of screw holes formed therein at a second end of the bonnet portion, wherein the second plurality of bonnet portion screw holes corresponds to the valve body screw holes. The operating stem extends through the bonnet portion central hole, and the operating stem has a first end removably coupled to the valve member. The operating stem has a threaded second end. The nut has an exterior shape adapted to slidably interfit with the slotted piston portion, and the nut has a threaded hole formed therein that is threadedly coupled with the threaded second end of the operating stem. Again, the first modular actuator portion is removably coupled to the second modular actuator portion with a first plurality of fasteners via the cylinder retainer screw holes and the first bonnet screw holes, and the first modular actuator portion can be separated from the second modular actuator portion without disassembling the first modular portion. The first plurality of fasteners may comprise cap screws, wherein the first bonnet portion screw holes have threads formed therein adapted to threadedly engage with the cap screws. In alternative, the first plurality of fasteners may comprise studs extending from the bonnet portion and fastener nuts adapted to threadedly engage with a threaded portion of the studs. Likewise, the first plurality of fasteners may comprise bolts with accompanying fastener nuts. The second modular actuator portion is removably coupled to the valve body with a second plurality of fasteners via the second bonnet screw holes and the valve body screw holes. The second plurality of fasteners may comprise cap screws, studs with corresponding fastener nuts, and/or bolts with accompanying fastener nuts. The valve member may be a gate valve.
In accordance with another aspect of the present invention, a method of disassembling a modular actuator component for accessing at least one seal in the modular actuator component is provided. The method comprises the following steps, the order of which may vary:
(i) loosening a plurality of fasteners that hold a first modular portion of the actuator component and a second modular portion of the actuator component together. The first modular actuator portion comprises: a hollow cylinder portion, a piston located in the cylinder portion, the piston being adapted to slidably fit in the cylinder portion, and the piston having a slotted portion formed therein, a piston retainer portion located at an interior surface of the cylinder portion and at a first end of the cylinder portion, wherein part of the piston retainer portion extends radially inward relative to the interior surface farther than a portion of the piston such that the piston cannot slide completely past the piston retainer portion, a cylinder head portion closing a second end of the cylinder portion, and a locking screw extending through the cylinder head portion and threadedly coupled to the cylinder head portion, the locking screw being adapted to press against the piston with a first end of the locking screw for displacing the piston. The second modular actuator portion comprises: a bonnet portion having a central hole formed therethrough, an operating stem extending through the bonnet portion central hole, the operating stem having a threaded end, a nut having an exterior shape that is slidably engaged with the slotted piston portion, and the nut having a threaded hole formed therein that threadedly interfits with the threaded operating stem end, and the at least one seal located about the operating stem;
(ii) displacing the piston towards the first end of the first modular portion until the slotted piston portion extends outside of the first modular portion;
(iii) preventing the piston from being completely slid out of the first modular portion through the first end of the cylinder portion with the piston retainer portion;
(iv) sliding the nut out of engagement with the slotted piston portion; and
(v) separating the first modular portion from the second modular portion.
The plurality of fasteners may comprise cap screws, and the method may further comprise the step of (vi) removing the cap screws after the loosening step. The second modular portion may have a plurality of studs extending therefrom, wherein the plurality of fasteners are fastener nuts adapted to threadedly engage the studs, and the method may further comprise the step of (vi) removing the fastener nuts. The plurality of fasteners may comprise bolts with accompanying fastener nuts, and the method may further comprise the step of (vi) removing the fastener nuts. Or, the plurality of fasteners may comprise a clamping mechanism, and the method may further comprise the step of (vi) opening the clamping mechanism. The second modular portion may further comprise a packing gland, the packing gland being located about the operating stem and threadedly engaged with the bonnet portion, wherein the packing gland retains the at least one seal, and the method may further comprise the step of (vi) unthreading and removing the packing gland from the second modular portion. Also, the second modular portion may further comprise a drift ring, the drift ring being located about the operating stem and threadedly engaged with the bonnet portion for the purpose of limiting the stroke of the piston when the actuator component is operably assembled, and the method may further comprise the step of (vii) unthreading and removing the drift ring from the second modular portion. The method may further comprise the step of removing the nut from the operating stem. During the displacing piston step, the locking screw may be rotated manually rotated via a handle coupled to the locking screw so that the locking screw moves toward the piston, presses against the piston, and displaces the piston.